Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters from 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather
By: Dr. Jeff Masters , 12:25 PM GMT on September 20, 2012
Tropical Storm Nadine is headed east-southeast at 10 mph, parallel to the Azores Islands, and tropical storm warnings continue for portions of the island chain. Nadine brought sustained winds of 26 mph, gusting to 38 mph to Horta Castelo Branco in the Azores at 8:30 am local time, and occasional heavy rain showers have affected most of the islands today. Nadine is a very large storm, as seen on visible satellite loops, and will affect the islands for at least two more days as it treks slowly to the southeast of the islands. On Friday, Nadine is expected to convert to an extratropical storm due to cool waters and the influence of an upper-level low. The final fate of Nadine is very uncertain; the extratropical version of Nadine could continue moving eastward towards Portugal early next week, or move back to the west-southwest and potentially become a tropical storm again.
Figure 1. Morning satellite image of Tropical Storm Nadine brushing the Azores (at right of image) and of an extratropical storm (94L) with a 40% chance of becoming a subtropical storm by Saturday (center of image.)
Extratropical storm 94L east of Bermuda may acquire tropical characteristics
A large, cold-cored extratropical storm about 700 hundred miles east of Bermuda (Invest 94L) has a well-defined surface circulation, and has been over warm waters long enough to develop a respectable amount of heavy thunderstorm activity, as seen on visible satellite loops. This low has the potential to become a warm-cored subtropical storm this week. Wind shear is a moderate 10 - 20 knots, but the low has plenty of cold, dry air aloft that is slowing down transition to a subtropical storm. The low is over warm waters of 28°C, but the waters under 94L will cool to 26.5°C by Saturday, as the system tracks to the west-northwest at 10 mph. 94L should turn to the north by this weekend and potentially affect the Canadian Maritime Provinces on Sunday. In their 8 am EDT Tropical Weather Outlook, NHC gave the storm a 40% chance of becoming a subtropical or tropical cyclone by Saturday morning.
Elsewhere in the tropical Atlantic, none of the reliable computer models is predicting tropical cyclone development through September 26.
I'll have a new post late this morning on Arctic and Antarctic sea ice.
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